Siemens NXAIR - Replacing Protection Fuse-Links for the Control Transformer

Operating the contactor panel with panel width 600 mm
110-0134.9 / 14 NXAIR / ≤ 40 kA 199
Requirements
The coordination of the components of the motor circuit requires the following:
• The let-through current I
D
must not exceed 46 kA at 7.2 kV.
• In case of low-voltage supply via a control transformer, short-circuit currents ranging above the limit
breaking capacity must be interrupted within 80 ms. This requirement does not apply if
• the mechanical latch is provided
or
• the opening times have been extended so much that – in the a.m. current range – the contactor
can only open when the fuse-link has interrupted the current.
• Due to the arising motor starting current, the instant when the motor starts represents the maximum
stress for the HV HRC fuse-link. This stress must neither operate nor pre-damage the fuse-link.
• Other factors of influence on the stress of the HV HRC fuse-links are the starting time and the
starting frequency of the motors.
14.22 Replacing protection fuse-links for the control transformer
Arrangement of protection fuse-links
The control transformer (2) is equipped with 2 protection fuse-links (1). The protection fuse-links are only
accessible after removing the HV HRC fuse-links from the outer phases.
Fig. 356: Rear side of truck: Arrangement of
protection fuse-links for control transformer
1
2